PPARGC1A and obesity due to melanocortin 4 receptor deficiency: In this obesity model, mitochondrial function of IEC and Pgc1a expression were not modified by WD consumption compared to chow fed mice. Furthermore, the expression of genes encoding TJ proteins, including Cldn2, were unaltered in IEC from WD mice and the expression of proliferative markers was diminished in WD mice compared to chow fed mice (Supplementary Fig. 5).